Electrical service disconnect having tamper detection

ABSTRACT

A tamper detection arrangement in a meter having a service disconnect switch employs a voltage sense circuit that requires only a single connection to digital processing circuitry for the feeder lines of typical residential service. In one embodiment, the voltage sense circuit includes an isolation device that electrically isolates the processing device from the line voltages. The voltage sense circuit senses a voltage on the feeder lines and is operable to generate a voltage detection signal having a characteristic representative of whether line voltage from the electrical power lines is present on the feeder lines. A processing circuit is operably connected to the voltage sense circuit to receive the voltage detection signal and to selectively generate a tamper flag based on whether the characteristic of the voltage detection signal indicates the presence of voltage on the first and second feeder lines when the service disconnect switch has disconnected the electrical power lines from the first and second feeder lines.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/272,023, filed Feb. 28, 2001, and which isincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to electricity meters, and moreparticularly to electricity meters that are used in conjunction withload disconnect devices.

BACKGROUND OF THE INVENTION

Electrical service providers such as electrical utilities employelectricity meters to monitor energy consumption by customers (or otherentities). Electricity meters track the amount of energy consumed a load(e.g. the customer), typically measured in kilowatt-hours (“kwh”), ateach customer's facility. The service provider uses the consumptioninformation primarily for billing, but also for resource allocationplanning and other purposes.

Electrical power is transmitted and delivered to load in many forms. Forexample, electrical power may be delivered as polyphase wye-connected ordelta-connected power or as single phase power. Such various forms areknown as service types. Different standard electricity meter types,known as meter forms, are used to measure the power consumption for thevarious service types. The commonly used meter forms in the UnitedStates include those designated as 2S, 3S, 5S, 45S, 6S, 36S, 9S, 16S,12S and 25S meter forms, which are well known in the art.

Electrical service providers have historically billed for electricalservice in arrears, using information stored within the electricitymeter to determine the amount of each invoice. In a typical operation,the electricity meter stores a value representative of the amount ofenergy consumed in a mechanical or electronic accumulation register.From time to time, the electrical service provider obtains the value ofthe register and bills the customer accordingly. For example, a meterreader employed by the service provider may, each month, physically readthe register value off a meter display. The service provider thenemploys the obtained register value to determine the amount ofelectricity consumed over the month and bills the customer for thedetermined amount.

A problem with the above-described operation of electrical serviceproviders arises from the fact that some customers are frequentlydelinquent in or, in default of, payments for electricity consumption.Because electrical service is billed in arrears, delinquent payments canresult in significant losses for the service provider.

In addition, interrupting the delivery of electrical power hashistorically been an expensive and significant event. Typically, atechnician must be dispatched to the customer's residence, or in thevicinity thereof, to physically disconnect the power. Accordingly, whilethe electrical service provider might physically disconnect the power tothe customer's facility for several months of complete payment default,physical disconnection is not practical in circumstances in whichcustomers are merely delinquent, or that can only pay portions of theirbills. In particular, the cost an effort of sending a technician out todisconnect electrical service is wasted if the customer pays a day ortwo later, thereby requiring another service call to restore service.

One method of controlling losses associated with delinquent customers isto require prepayment for services. In prepayment arrangements,customers use prepaid debit cards or credit cards to “purchase” energyin advance. When the purchased energy has been consumed, the electricalservice is disconnected. Thus, the service provider is not exposed toextended periods of electrical service for which no payment may beprovided. Another method of handling delinquent customers is tointermittently interrupt power to delinquent customers until the pastdue payments are made. Intermittent interruptions tend to reduce theamount of energy consumed by the delinquent payor, thus advantageouslyreducing utility provider losses while also reducing bills to thedelinquent payor.

Each of the above methods, however, typically requires the ability todisconnect and/or reconnect the customer's power without a technicianservice call to the customer's location. For example, in a prepaymentscenario, the service provider must have a method of disconnecting poweronce the prepaid amount of energy has been consumed. Similarly, theintermittent interruption technique requires frequent connection anddisconnection of the electrical service.

One technique for automated or remote service disconnection is to employa service disconnect switch device within an electricity meter. Theservice disconnect switch is a relay or other device that controllablydisconnects and re-connects the utility power lines to the customer'sfeeder lines, thereby controllably interrupting power to the customer'sfacility. In some cases, the service disconnect switch is tripped by aremote device that communicates with the electricity meter circuitrythrough a modem, radio or the like. Alternatively, such as in the caseof prepayment, the meter itself may be programmed to disconnect andreconnect electrical service under certain circumstances. In somesituations, the meter may disconnect and restore electrical servicethrough a combination of local programming and remote commands.

Thus, the inclusion of a service disconnect switch within a meterfacilitates various methods and techniques for providing electricalservice to parties that have poor payment records. Such methods andtechniques advantageously do not require a permanent disconnection by afield technician. The conveniences provided by a service disconnectswitch also extends beyond use in connection with delinquent payors. Forexample, electrical energy rationing may be implemented using techniquesenabled by the service disconnect switch.

Nevertheless, various issues that arise from the use of a servicedisconnect switch have not been adequately addressed in the prior art.For example, many of the above described service interruption techniquestypically require automated reconnection to be truly viable. In otherwords, if a technician must be dispatched every time power is to bereconnected to a customer after a service interruption, the convenienceand cost advantages of the automated disconnection are significantlyreduced.

Automatic reconnection of a customer's facility to electrical servicecan raise potential dangers. For example, consider a situation in whichthe customer is operating a clothes iron or electric stove whenelectrical service is disconnected. If the customer does not remember toturn such a device off during the electrical service interruption, thenthe device will automatically resume operating again (at hightemperatures) when power is restored. The automatic restoration of ironor stove operation can create a fire hazard, particularly if thecustomer has since become otherwise occupied or has left the premises.Accordingly, restoring power through an automatically operated servicedisconnection switch raises some safety issues, as well as other issues.

In addition to safety issues, a drawback of service disconnect switchesis that they may be defeated through tampering either within or externalto the meter. Such tampering typically involves placing a bypass aroundthe service disconnect switch. The bypass provides a path through whichthe customer may receive electrical power even though the servicedisconnect switch has been opened.

One prior art device disclosed in U.S. Pat. No. 5,940,009 detects suchtampering by detecting a voltage signal on the load-side connection of adisconnect switch. In particular, this prior art device connects theload-side customer feeder lines to a processor through a voltagedivider. The processor then interprets the waveforms of from multiplefeeder lines to determine whether power is still being provided to theload even when a service disconnect switch has disconnected the serviceto the customer's load. The drawback of the device disclosed in U.S.Pat. No. 5,940,009 is that it requires multiple inputs to amicroprocessor to monitor multiple feeder lines, and further exposes themicroprocessor directly to the power line signals, albeit through avoltage divider.

Other issues with service disconnect devices within meters includewhether and how a disconnect switch could be implemented in a modularmeter. Modular meters are those that include separable components. Oneremovable component includes much of the meter electronic and processingcircuitry while the other component contains high voltage sensorcircuitry that interconnects with the power lines. Modular meters allowfor easy enhancement of meter features and operations becausereplacement of the removable component that includes the meterelectronic and processing circuitry typically suffices for suchenhancements. Thus, to obtain improved functionality, only a portion ofthe meter must be replaced. Service disconnect switches do not readilylend themselves to modular meters because service disconnect switchesrequire both electronic and high power components, which are typicallyseparated into different modules of the modular meter.

There is a need, therefore, for an electricity meter that employsservice disconnect switch and that avoids one or more of the abovedescribed drawbacks. In particular, a need exists for an electricitymeter that includes a service disconnect switch having increased safetyenhancements associated with reconnecting a customer's electricalservice after an interruption. A need exists for an electricity meterthat obtains the benefits of both modularity in a meter and the use ofan automatically operated service disconnect switch within a meter.

SUMMARY OF THE INVENTION

The present invention fulfills the above needs, as well as others, byproviding a tamper detection arrangement in a meter having a servicedisconnect switch that employs a voltage sense circuit that requiresonly a single connection to digital processing circuitry for the twolines of typical residential service. In a preferred embodiment, thevoltage sense circuit includes an isolation device that electricallyisolates the processing device from the line voltages.

In one embodiment of the invention, an apparatus for determiningtampering in an electricity meter arrangement is provided that comprisesa service disconnect switch operable to controllably disconnectelectrical power lines from a load including at least first and secondfeeder lines. The arrangement further includes a voltage sense circuitcoupled to sense voltage on the first and second feeder lines, in whichthe voltage sense circuit is operable to generate a voltage detectionsignal based on a first voltage on the first feeder line and a secondvoltage on the second feeder line. In one feature of the invention, thevoltage detection signal has a characteristic representative of whetherline voltage from the electrical power lines is present on the first andsecond feeder lines.

The arrangement further includes a processing circuit that is operablyconnected to the voltage sense circuit to receive the voltage detectionsignal. In accordance with the invention, the processing circuit isoperable to selectively generate a tamper flag based on whether thecharacteristic of the voltage detection signal indicates the presence ofvoltage on the first and second feeder lines when the service disconnectswitch has disconnected the electrical power lines from the first andsecond feeder lines.

In a further embodiment of the invention, an apparatus for determiningtampering in an electricity meter arrangement comprises a housingcontaining a metering circuit and a service disconnect switch disposedwithin the housing. The service disconnect switch is operable tocontrollably disconnect electrical power lines from a load, the loadincluding at least first and second feeder lines. In one aspect of thisembodiment, a voltage sense circuit is coupled to sense voltage on atleast one feeder line, the voltage sense circuit including an isolationmechanism interposed between the at least one feeder line and an output.The voltage sense circuit is operable to generate a voltage detectionsignal having a characteristic representative of whether line voltagefrom the electrical power lines is present on the at least one feederline, and is further operable to provide the voltage detection signal tothe output. The apparatus can further include a processing circuitoperably connected to the output to receive the voltage detection signaland to selectively generate a tamper flag based on whether thecharacteristic of the voltage detection signal indicates the presence ofvoltage on the at least one feeder line when the service disconnectswitch has disconnected the electrical power lines from the first andsecond feeder lines.

A further embodiment of the invention contemplates a method comprisingthe step of disconnecting, using a service disconnect switch, at leastone feeder line of a load from at least one electrical power line, theservice disconnect switch disposed within an electricity meter housing.Another step of the method includes employing a voltage sense circuitoperably connected to the at least one power line to generate a voltagedetection signal having a characteristic representative of whether linevoltage from the electrical power lines is present on the at least onefeeder line. The voltage detection signal is provided to an output thatis electrically isolated from the at least one feeder line. In a furtherstep, a processing circuit can be employed to receive the voltagedetection signal and generate a tamper flag if the characteristic of thevoltage detection signal indicates the presence of line voltage on theat least one feeder line.

In another feature, the voltage sense circuit can be employed togenerate the voltage detection signal such that the voltage detectionsignal has a first magnitude when line voltage is present on the atleast one feeder lines and the voltage detection signal has a secondmagnitude when line voltage is absent from the at least one feeder line.In still another feature, the voltage sense circuit can be employed togenerate the voltage detection signal such that the first magnitude andthe second magnitude are discrete digital voltage levels.

The above described features and advantages, as well as others, willbecome more readily apparent to those of ordinary skill in the art byreference to the following detailed description and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an exemplary meter having a servicedisconnect circuit arrangement in accordance with aspects of the presentinvention;

FIG. 2 shows an exploded perspective view of an exemplary embodiment ofa modular electricity meter that may incorporate a service disconnectarrangement in accordance with aspects of the present invention;

FIG. 3 shows a perspective view of the modular electricity meter of FIG.2 implemented in an exemplary meter mounting device;

FIG. 4 shows a perspective view of a service disconnect switch modulefor use in the modular electricity meter of FIG. 2;

FIG. 5 shows a perspective view of an external interface assembly foruse in the modular electricity meter of FIG. 2;

FIG. 6 shows a schematic diagram of the sensor module of the modularelectricity meter of FIG. 2;

FIG. 7 shows a schematic diagram of the driver circuit of the sensormodule of FIG. 6;

FIG. 8 shows a schematic diagram of the measurement module of themodular electricity meter of FIG. 2.

DETAILED DESCRIPTION

Referring now to the drawings, and more particularly to FIG. 1, adiagram of an electrical utility meter 100 constructed according toaspects of the present invention is shown. In FIG. 1, the meter 100 isoperably coupled to utility power lines 102. The utility power lines 102are connected to a source of electricity, such as a power transmissionand distribution system, not shown. A load 104 (typically a consumer ofelectrical power) is connected to the power lines 102 through feederlines 106. The meter 100 is operably coupled to the feeder lines 106 todetect the amount of electricity delivered to the load. The meter 100 isoperable to, among other things, generate metering informationrepresentative of a quantity of electrical energy delivered to the load104.

A housing assembly 112 is disposed over the meter 100 and encasesvarious components thereof. Voltage sensors 114 and current sensors 116are secured within the housing assembly 112, and are operable to receivevoltage and current signals representative of voltage and currentprovided to the load 104 and generate measurement signals therefrom. Inparticular, the measurement signals generated by the voltage sensors 114and current sensors 116 are analog signals each having a waveformrepresentative of the voltage and current provided to the load 104. Forpurposes of example and explanation, FIG. 1 illustrates two voltagesensors 114 and current sensors 116 for generating measurement signalsfor two-phase electrical service, or for two sides of a 240-voltsingle-phase three-wire electrical service. However, it will beintuitive to those skilled in the art that the principles of the presentinvention may also be applied to three-phase power systems.

A processing circuit 118 is operable to receive the analog measurementsignals from the voltage sensors 114 and the current sensors 116 andgenerate energy consumption data therefrom. According to an exemplaryembodiment, the processing circuit 118 includes analog interfacecircuitry 118 a that receives and digitizes the measurement signals, anddigital processing circuitry 118 b that processes the digitizedmeasurement signals to thereby generate the energy consumption data.Such circuits are well known in the art. According to an alternativeembodiment, however, the processing circuit 118 generates the energyconsumption data by operating directly upon the analog measurementsignals. As is known in the art, the processing circuit 118 may includeone or more integrated circuits.

The meter 100 includes a service disconnect circuit 120 that includesone or more service disconnect switches 120 a and a logical controlportion 120 b. It will be appreciated that the logical control portion120 b and the processing circuit 118 may suitably share some or all ofthe same components and/or circuitry. However, in other embodimentsincluding the one described below in connection with FIGS. 2 through 8,the control portion of the service disconnect circuit and the processingcircuit of the meter are completely distinct circuits. It will also beappreciated that the control portion 120 b and the service disconnectswitch 120 a may be housed in a single structure. However, in theembodiment of FIGS. 2 through 8, the control portion located on acircuit board that is distinct from the service disconnect switch.

Referring again to FIG. 1, one or more service disconnect switches 120 aare operably coupled to the processing circuit 118 within the housingassembly 112, and selectively connect and disconnect the power lines 102to the load 104 under the control of the processing circuit 118. Ingeneral, the service disconnect circuit 120 has a connected state, adisconnected state, and an armed state. The states of the servicedisconnect circuit 120 are maintained within the control portion 120 b.The control portion 120 b controls the service disconnect switches 120 ain accordance with the state logic.

More specifically, in the connected state, the service disconnect switch120 a operably couples the power lines 102 to the load 104 so as toprovide electrical power thereto. In the disconnected and armed states,the service disconnect switch 120 a operably decouples the power lines102 from the load 104 so as to remove the supply of electrical powertherefrom. Indeed, the control circuitry of the service disconnectswitch may constitute a portion of the processing circuit 118 of themeter.

The service disconnect circuit 120 changes from the connected state tothe disconnected state in response to a first signal received from theprocessing circuit 118, and changes from the disconnected state to thearmed state in response to a second signal within the processing circuit118. It should be noted that the signals that cause the state changesmay be provided on one or more physical line A communication circuit 122is operably coupled to the processing circuit 118, and is also operableto receive signals from a remote device 124. The communication circuit122 may, for example, receive signals from the remote device 124 via atangible communication link (e.g., cable, wire, fiber, etc.), or via awireless communication link. According to one aspect of the invention,the communication circuit 122 is operable to receive a disconnect signalfrom the remote device 124. In response to the disconnect signal, thecommunication circuit 122 provides information representative of thedisconnect signal to the processing circuit 118. The processing circuit118 in turn provides the first signal to the control portion 120 b ofservice disconnect circuit 120, Thereby causing the service disconnectcircuit 120 to change from the connected state to the disconnectedstate. In the disconnected state, the service disconnect switches 120 adisconnect the feeder lines 106 from the power lines 102.

According to another aspect of the invention, the communication circuit122 is operable to receive an arm signal from the remote device 124. Inresponse to the arm signal, the communication circuit 122 providesinformation representative of the arm signal to the processing circuit118. The processing circuit 118 in turn provides the second signal tothe service disconnect circuit 120, thereby causing the servicedisconnect circuit 120 to change from the disconnected state to thearmed state. In the armed state, as discussed above, the switches 120 ado not immediately reconnect the feeder line 106 to the power lines 102.

As will be more fully discussed below, the service disconnect circuit120 changes from the armed state to the connected state responsive toactuation of an externally accessible actuator 130.

One or more electronic indicators 126 are operably coupled to thecontrol portion 120 a and provide visual signals regarding operation ofthe service disconnect circuit 120. Each indicator 126 may, for example,be embodied as an indicator lamp including a light emitting diode, or asa liquid crystal display segment. According to an exemplary embodiment,each indicator 126 is visible external to the housing assembly 112 andis operable to provide a visual signal representative of the currentstate of the service disconnect circuit 120. For example, the indicator126 may include a first indicator lamp that provides a visual signalindicative of one or more service disconnect switches 120 in the armedstate, and a second indicator lamp that provides a visual signalindicative of one or more service disconnect switches 120 in thedisconnected state. Alternatively, the indicator 126 may be embodied asa single element which provides a first visual signal indicative of oneor more service disconnect switches 120 in the armed state, and a secondvisual signal indicative of one or more service disconnect switches 120in the disconnected state. It will be appreciated that in alternativeembodiments, the indicators 126 may be connected to the processingcircuit 118 as opposed to the control portion 120 a of the servicedisconnect circuit 120.

A display 128 is operably coupled to the processing unit 118 andprovides a visual display of information, such as information regardingthe operation of the meter 100. For example, the display 128 may providea visual display regarding the power measurement operations of the meter100. The display 128 and the indicator 126 may be separate and distinctelements of the meter 100, as shown in FIG. 1, or may be combined into asingle display unit.

An actuator 130 is operably coupled to each service disconnect switch120. When actuated, the actuator 130 causes one or more servicedisconnect switches 120 to change from the armed state to the connectedstate. The actuator 130 is coupled to the control portion 120 b of theservice disconnect switch 120, or may be directly coupled to eachservice disconnect switch 120. The actuator 130 is preferably disposedon the housing assembly 112, and is accessible from an external portionof the housing assembly 112. The actuator 130 may, for example, beembodied as one or more pushbutton mechanisms or other elements that maybe actuated by a user.

A voltage sense circuit 132 is coupled to sense voltage on one or moreof the feeder lines 106. According to an exemplary embodiment, thevoltage sense circuit 132 generates a voltage detection signal based ona first voltage on one feeder line 106 and a second voltage on the otherfeeder line 106. The voltage detection signal has a characteristicrepresentative of whether line voltage from the power lines 102 ispresent on one or more of the feeder lines 106. For example, the voltagesense circuit 132 generates the voltage detection signal having a firstmagnitude when line voltage is present on one or more of the feederlines 106, and having a second magnitude when line voltage is notpresent on one or more of the feeder lines 106. The first and secondmagnitudes of the voltage detection signal may correspond to discretedigital signal levels.

The processing circuit 118 is operably coupled to the voltage sensecircuit 132 to receive the voltage detection signal. The processingcircuit 118 selectively generates a tamper flag based on whether thevoltage detection signal indicates the presence of voltage on one ormore of the feeder lines 106 when one or more service disconnectswitches 120 has disconnected the power lines 102 from one or more ofthe feeder lines 106.

The above-described meter 100 thus incorporates the advantages of havingthe externally accessible actuator 130, namely, to allow for restorationof power after a disconnection by the service disconnect switch thatrequires customer-side participation. As discussed above, such arequirement enhances safety by effectively preventing the restoration ofpower by the service disconnect switch when no one is present at thecustomer's facility. The advantages of the externally accessibleactuator are enhanced through the optional use of electronic indicatorsthat signal to the customer that the disconnect switch is armed and thatpower may be restored.

The above-described meter 100 also provides an improved tamperprotection system that requires fewer connections to the digitalprocessing circuitry and preferably isolates the digital processingcircuitry from the power lines. In particular, by generating a singlevoltage detection signal based on the measurement of multiple feederlines, fewer inputs in a digital processing device need to be dedicatedto the operation of that circuit. It will be appreciated that theadvantages provided by improved tamper system may be obtained in metersthat do not include the externally accessible actuator described above.Similarly, it will be appreciated that the advantages provided by theexternally accessible actuator may be obtained in meters that do notinclude the improved tamper system described above.

While the above-described features provide at least some advantages inany electricity meter that includes a service disconnect switch, furtheradvantages may be obtained through the implementation of such featuresin a modular electricity meter. FIGS. 2 through 8 show an exemplaryembodiment of a modular electricity meter 10 that incorporates severalaspects of the present invention.

In particular, FIG. 2 shows an exploded view of a modular meter 10. Ingeneral, the meter 10 includes a sensor module 12 and a measurementmodule 14. The measurement module 14 is constructed such that it may beremovably coupled to the sensor module 12. The measurement module 14 andthe sensor module 12 cooperate to form a type of revenue meter known inthe revenue metering industry as a single-phase meter form. Thesingle-phase meter form is the type typically employed for stand-alonesingle-family dwellings. It will be noted, however, that the presentinvention is not limited to single phase metering applications, but mayreadily be incorporated into polyphase meter forms including, forexample the commonly known 1S, 12S, and 25S meter forms.

The sensor module 12 includes voltage and current sensors, whichaccording to the exemplary embodiment described herein, include firstand second current transformers 16 a and 16 b, a plurality of currentblades 22 a, 22 b, 24 a, 24 b (current blade 22 b shown in FIG. 4), andone or more neutral blades 20. The current blades 22 a, 22 b, 24 a, and24 b are secured to the housing of a service disconnect switch 25. As isknown in the art the service disconnect switch 25 may suitably be anelectrically controlled relay. FIG. 4 shows a perspective view of theservice disconnect switch 25 and the current blades 22 a, 22 b, 24 a and24 b in further detail. As shown in FIG. 4, the service disconnectswitch 25 includes a housing 60 which houses the actual switchingrelays, not shown. Extending from the housing are lead wires 62 andconnection terminals 64 that provide the control connections to therelays inside of the housing.

In the exemplary embodiment described herein, the service disconnectswitch 25 includes a 200 amp latching relay, such as one commerciallyavailable from BLP of the United Kingdom. The latching relay has thecharacteristic of changing state (closed to open or open to closed) uponreceipt of a characteristic input signal, and then retaining the statewhen the signal is removed, only changing state upon receipt of adifferent characteristic signal. However, in other embodiments, anormally open or normally closed relay may be employed, although at someloss of efficiency. The use of a 200-amp relay corresponds to thetypical 200 amp residential electrical service. Relays having othercapacities may be used if desired to accommodate electrical servicerated at a different quantity of amps.

Further detail regarding the electrical connections between the currentblades 22 a, 22 b, 24 a, and 24 b is and the service disconnect switch25 is provided below in connection with FIG. 6, which shows a schematicdiagram of sensor module 12.

The current blades 22 a, 22 b, 24 a and 24 b are configured to bereceived by jaws of a standard meter mounting device. FIG. 3 shows,among other things, an exemplary meter mounting device including jaws 22in which the current blades 22 a, 22 b, 24 a and 24 b are received.

The first and second current transformers 16 a and 16 b, respectively,are preferably toroidal transformers having a substantially circularshape defined by a circular core. In the present embodiment, the firstcurrent transformer 16 a has a turns ratio of N1 and the second currenttransformer 16 b has a turns ratio of N2. The current blade 22 a passesthrough the interior of the toroid formed by the first currenttransformer 16 a and the current blade 22 b passes through the interiorof the toroid formed by the second current transformer 16 b.Accordingly, the current transformers 16 a and 16 b are in a currentsensing relationship with the current blades 22 a and 22 b,respectively.

Also enclosed within the housing 12 a of the sensor module 12 is adriver circuit board 23 and an interface assembly 27. The driver circuitboard 23 provides the structure on which is disposed the driver circuit(illustrated in FIG. 7). The driver circuit board 23 includes first andsecond actuators 78 and 80, discussed in additional detail furtherbelow. The driver circuit board 23 further includes a ribbon connectorassembly 88. The ribbon connector assembly includes a first connectorblock 88 a secured to the driver circuit board 23, a ribbon connector 88b, and a second connector block 88 c for connection to the measurementcircuit of the measurement module 14. The interface assembly 27 is asubassembly that includes a plurality of indicators 52, 54, a pushbuttonactuator 56, and corresponding lead wires 58.

More specifically, FIG. 5 shows the interface assembly 27 and anunderside view of the housing 12 a. Referring to FIG. 5, the housing 12a is shown without any of the elements mounted therein for purposes ofclarity of exposition of the connection of the interface assembly 27 tothe housing 12 a. In general, the housing 12 a is preferably a moldedplastic cylindrical shaped container for receiving the components of thesensor assembly 12 illustrated in FIG. 2. Referring again to FIG. 5, thehousing 12 a includes, on an inner side thereof, a molded seatingstructure 66 designed to receive the interface assembly 27 therein. Themolded seating structure 66 is integrally molded with the housing 12 aproximate the periphery of the housing 12 a adjacent apertures 68, 70and 72. The apertures 68, 70 and 72 provide openings from the interiorof the housing 12 a through which the indicators 52, 54 may be viewedand through which external access to the actuator 56 is provided.

In particular, when the interface assembly 27 is seated within themolded seating structure 66, the indicators 52, 54 extend partially intoor through the apertures 68, 70 respectively and the actuator 56 extendspartially through the aperture 72. Because the apertures 68, 70 and 72provide communication between the interior of the sensor housing 12 aand the exterior, arrangements are provided to isolate the interior ofthe sensor housing 12 a from significant exposure to externalcontaminants, moisture and the like. To this end, the interface assembly27 includes an elastomeric boot or seal 74 that extends over theactuator 56. The elastomeric seal 74 includes a base 74 a that is wedgedbetween a U-shaped switch bracket 76 and one or more sealing washers 79within the seating structure 66. The actuator 56 and the seal 74 extendat least partially through the aperture 72 to the exterior of thehousing 12 a. In this position, a person external to the meter 10 mayactuate the actuator 56 by depressing the elastomeric seal 74 andactuator 56. The seal 74 and the sealing washers 79 allow for externaloperation of the movable actuator 56 without exposing the interior ofthe housing, which includes high voltage and current components, tosignificant amounts of environmental moisture or contaminants.

To inhibit contamination or moisture ingress through the apertures 68and 70, first and second sealing lenses 52 a and 54 a are provided thatextend over the indicators 52 and 54, respectively. The lenses 52 a and54 a provide the necessary sealing function while also permitting thelight from the indicators 52 and 54 to radiate therethrough.

The sensor module 12 further includes an electrically safe interface 26.The electrically safe interface 26 comprises a first interconnectingmeans for connecting to the measurement module 14. The electrically safeinterface 26 also includes means for preventing physical contact of ahuman operator with potentially hazardous electrical signals present onat least a portion of the voltage and current sensors 15. Signal levelswhich are considered potentially hazardous are well known. Differentlevels of potential hazard also exist. For example, signals capable ofgenerating shock currents exceeding 70 milliamperes are possible burnhazards, while signals generating shock currents on the order of 300milliamperes may constitute life-threatening hazards. Furthermore,signals generating shock currents as low as 0.5 to 5 milliamperes areknown to cause an involuntary startle reaction.

In revenue meters, at least some of the sensor devices carry suchpotentially hazardous electrical signals. Specifically, any portion of ameter that is electrically connected to the voltage and current signalsfrom the power line constitutes a life-threatening hazard. Theelectricity meter 10 of the present invention isolates the voltage andcurrent sensors by placing them within the meter mounting device 13 andproviding the electrically safe interface 26. In the present embodiment,the current blades 22 a, 22 b, 24 a and 24 b are directly connected tothe facility power line and therefore must be isolated. Although otherportions of the sensors 15 may not be directly connected to the powerlines, the electrically safe interface 26 preferably prevents humancontact with all of the voltage and current sensors 15 as a safetymeasure.

In the present embodiment, the means for preventing physical contactincludes a top plate 28, a plurality of sockets 30 a, 30 b, 30 c, 30 d,30 e, 30 f and 30 g, the actuators 78 and 80 and the connector block 88a of the driver circuit board 23. Each of the sockets 30 a through 30 gdefines an opening in the top plate 28. Two other openings in the topplate 28 include actuator openings 82 and 84 which receive the actuators78 and 80 from the driver circuit board 23. Yet another opening in thetop plate 28 is a connector opening 86 through which the connector block88 a of the driver circuit board 23 extends. Other than theabove-described openings, the top plate 28 preferably forms a completebarrier or wall from the measurement module 14 to the voltage andcurrent sensors 15.

At a minimum, the top plate 28 operates to prevent human contact withthe portions of the voltage and current sensors 15 that directly contactthe power lines of the facility, and in particular, the current blades22 a, 22 b, 24 a and 24 b.

In order to provide a complete barrier, the top plate 28 cooperates withthe enclosure base 16 and a cover of a cooperating meter mounting device(See, e.g. FIG. 3) that enclose the voltage and current sensors 15 fromthe side and bottom. In another alternative embodiment, the top plate 28may be integrally coupled to such a cover.

Referring again to FIG. 2, the sockets 30 a through 30 g and theircorresponding openings are preferably configured to prevent a humanoperator from physically contacting the electrically conductive portionsof the socket. In particular, the openings defined by the sockets 30 athrough 30 g have sufficiently small proportions to prevent contact of astandard test finger with the electrically conductive portions of thesockets 30 a through 30 g. A standard test finger is a mechanical deviceused in the electrical industry to determine whether an electricalconnection socket is safe from accidental contact by a human finger. Onestandard test finger is described in Underwriter's Laboratory, Inc.,Standard for Safety of Information Technology Equipment IncludingElectrical Equipment Business UL-1950 (Feb. 26, 1993).

In the present embodiment, the openings defined by the sockets 30 athrough 30 g preferably have a first dimension, for example, the length,and a second dimension, for example, the width, wherein the firstdimension has at least the same size as the second dimension, and thesecond dimension is less than ⅛ inch, thereby preventing substantialaccess of a human operator through the openings.

As will be discussed below, one of the advantages of the above describedsensor module 12 arises from the inclusion of the actuators 78 and 80that are accessible on the electrically safe interface 26. Theelectrically safe interface 26 is generally inaccessible to customersand other parties because it is typically covered or closed off by themeasurement module 14 when the meter 10 is assembled and operational.Accordingly, the actuators 78 and 80 are accessible only to personsauthorized to remove the measurement module 14.

The actuators 78 and 80 in the present embodiment provide signals thatcan disconnect (open) and arm the service disconnect switch 25. In adevice without a separate “armed” state, the actuators 78 and 80 may becoupled directly to the switch 25 to either open or close the switch 25.In any event, the actuators 78 and 80 provide a convenient and intuitivemeans by which an authorized technician may manipulate the servicedisconnect switch 25 without allowing customer access to such means.

The measurement module 14 comprises a face cover 32, a printed circuitboard 34, and a gasket 36. The printed circuit board 34 includes adisplay 38, and a measurement circuit. FIG. 8, discussed further below,shows a schematic block diagram of a measurement circuit 42 that mayreadily be used as the measurement circuit on the printed circuit board34 of FIG. 2. The measurement circuit is operable to receive measurementsignals and generate energy consumption data therefrom. The measurementcircuit is operably connected to provide the energy consumption data tothe display 38.

The measurement module 14 further includes second interconnecting meansoperable to cooperate with first interconnecting means (on the sensormodule 12) to connect the measurement circuit of the printed circuitboard 34 to the voltage and current sensors 15. For example, in thepresent embodiment, the measurement module 14 includes a plurality ofplugs 40 a through 40 g that are received by the corresponding pluralityof sockets 30 a through 30 g. The plurality of plugs 40 a through 40 g,when assembled, are electrically connected to the measurement circuitand physically connected to the printed circuit board 34. The printedcircuit board 34 further includes a block, not shown, configured toreceive the connector block 88 c of the connector assembly 88.

FIG. 3 shows an installation configuration that includes the meter 10and a meter box 13 comprising a housing 16 and a cover 18. The housing16 is box-like in structure having an opening for receiving the cover 18and a cabling opening 24 for receiving the power lines of the electricalsystem being metered, not shown. It will be appreciated that the housing16 need not be box-like in structure, and that any other suitable shapemay be used, as long as there is an opening for receiving a cooperatingmeter box cover and a cabling opening. The housing 16 further includesan interior 20. Within the interior 20 are located a plurality of jaws22 constructed of electrically conductive material. When installed intoa facility, the plurality of jaws 22 are electrically connected to thepower lines of the electrical system of the facility.

The plurality of jaws 22 receive and provide electrical connection tothe current blades 22 a, 24 a, 22 b and 24 b (see FIG. 2) as well as theneutral blade or blades 20. The relationship of the jaws and the blades22 a, 24 a, 22 b, and 24 b also define the alignment of the sensormodule 12 within the housing 16. Once the blades 22 a, 24 a, 22 b, and24 b (see FIG. 2) are engaged with the plurality of jaws 22 (FIG. 3),the sensor module 12 is installed within the interior 20 of the housing16. The cover 18 is then installed onto the housing 16. The cover 18includes a meter opening 18 a having a perimeter defined by theperimeter of the sensor module 12. Preferably, the perimeter of themeter opening 118 a has substantially the same shape and is slightlysmaller than the perimeter of the sensor module 12 such that the sensormodule 12 cannot be removed when the cover 18 is engaged with thehousing 16.

Once the cover 18 is installed, the measurement module 14 in the presentembodiment is placed in engagement with the sensor module 12 through themeter opening 18 a of the meter box cover 18. Prior to such engagement,the connector block 88 c of the ribbon connector assembly 88 is coupledto the corresponding connector, not shown, on the measurement module 14.After connection of the connector block 88 c, the measurement module 14is aligned over the sensor module 12 and then coupled thereto. When inengagement, the plugs 40 a through 40 g of the measurement module 14 areelectrically connected to the sockets 30 a through 30 g, respectively,of the sensor module 12.

In particular, as discussed above, the top plate 28 includes a pluralityof sockets 30 a, 30 b, 30 c, 30 e, 30 f and 30 g. Each socket 30 x hasan opening for receiving a corresponding plug 40 x that is preferablyslightly conical to allow for alignment adjustment of the plug 40×duringassembly of the measurement module 14 onto the sensor module 12. Thesocket 30 x, which may suitably include a spring loaded terminal, iselectrically connected to one of the current blades 24 a or 24 b for thepurposes of obtaining a corresponding phase voltage measurement, as willbe more fully discussed below.

Each plug 40 x is connected to the circuit board 34 and is configured tobe inserted the socket 30 x. The socket 30 x physically engages the plug40 x in such a manner as to provide an electrical connectiontherebetween. To this end, the plug 40 x may suitably be an ordinaryconductive pin. Further detail regarding the sockets 30 x, the plugs 40x, and an exemplary illustration of their structure andinterrelationship may be found in U.S. Pat. No. 5,933,004, which isincorporated herein by reference.

Once the measurement module 14, the cover 18, the sensor module 12, andthe housing 16 are all assembled as described above, the meter 10 (i.e.,the sensor module 12 and the measurement module 14) performs energyconsumption measurements on the electrical system of the facility.

It is noted that the meter 10 preferably includes one or more devices orarrangements that inhibit tampering. As discussed above in connectionwith FIG. 1, one method of tampering involves bypassing the meter 10and/or the service disconnect switch 25 in the sensor module 12. Devicesfor inhibiting such tampering are discussed in further detail below inconnection with FIGS. 6, 7 and 8. However, another method of tamperingwith a modular meter such as the meter 10 is to remove the measurementmodule 14 so that energy flowing through the sensor module 12 is notrecorded in the measurement circuit.

In particular, it is noted that if the measurement module 14 is removedfrom the sensor module 12, the facility to which the meter 10 isconnected will continue to receive electrical power service, but willnot be charged for such power usage. The facility will not be chargedfor such power usage because the billing information is generallyobtained from the energy consumption data in the measurement module 14,and the measurement module 14 does not generate any energy consumptiondata when the measurement module 14 is removed from the sensor module12. Accordingly, a potential method of meter tampering is to remove themeasurement module 14 from the sensor module 12 for a few hours a day,or for one or more days, and then replace the measurement module 14before utility service provider personnel comes to read the meter.

Exemplary arrangements for preventing such tampering in a modular metersuch as the meter 10 are disclosed in U.S. Pat. No. 6,275,168 and U.S.patent application Ser. No. 09/667,888, filed Sep. 22, 2000, both ofwhich are assigned to the assignee of the present invention and areincorporated herein by reference. In the alternative or in addition,electronic arrangements that detect and record removal of themeasurement module 14 may be employed, such as that described in U.S.patent application Ser. No. 09/345,696, filed Jun. 30, 1999, which isalso incorporated herein by reference. Such arrangements typicallygenerate a mechanical or electronic record indicating that themeasurement module 14 has been removed, so that tampering becomesevident to the utility.

The configuration of the meter box 13 in FIG. 3 is a standard mountingdevice known as a ringless-type mounting device. It will be noted thatthe meter 10 may readily be adapted for use in a ring-type mountingdevice as well. A ring-type mounting device differs from the meter box13 in FIG. 3 in that the sensor module 12 would be installed after themeter box cover 18 is assembled onto the housing 16. An annular ringwould then be used to secure the sensor module 12 to the meter box cover18. To this end, the standard meter box cover for use in a ring typemounting device includes a feature annularly disposed around the opening18 a which cooperates with the annular ring to engage and secure thesensor module 12 thereto.

It can thus be seen by reference to FIGS. 2 and 3, that the electricallysafe interface 26, when fitted to the meter mounting device housing 16and the cover 18, provides a substantially solid barrier between a humanoperator or technician and the current and voltage sensing devices whenthe measurement module 14 is removed for repair or replacement. The onlyopenings in the interface are of insufficient size to receive a humanfinger. The openings 82, 84 and 86 are closed off by, respectively, theactuators 78, 80 and the connector block 88 a. The openings thatcorrespond to the sockets 30 a through 30 g are sufficiently smallenough, and the sockets are sufficiently recessed within the openings,to prevent an operator from coming into direct contact with dangeroushigh voltages. In addition, even if the connector block 88 a is removed,the operator or technician is only exposed to a pin array (see pin array221 of FIG. 7). In accordance with the exemplary embodiment describedherein, the pin array contains only non-hazardous voltages, preferablyisolated from the utility power lines (see pin array 221 of FIG. 7).

It will be appreciated that other interconnection means may be employedin the sensor module 12 and measurement module 14 that will also providean electrically safe interface. For example, wireless means may be usedas the interconnection means. Such wireless means could provide voltageand current measurement signals from the sensor module 12 to themeasurement module 14. For example, the measurement module 14 couldinclude sensitive electric and magnetic field sensors that obtainvoltage and current measurement information from electromagneticradiation from the current and voltage sensors 15. Likewise, opticalcommunication means may be used to provide measurement signalinformation from the sensor module 12 to the measurement module 14. Inany case, the electrically safe interface would typically include abarrier such as the top plate 28 that prevents physical access by ahuman operator to the dangerous portions of the voltage and currentsensors 15 when the measurement module 14 is removed.

To fully obtain the benefits of modularity, it is necessary to addresscalibration issues in the design of the meter assembly 10. Specifically,the sensor module 12 preferably has a calibration feature that allows itto be used in connection with any suitable measurement module.

By contrast, in traditional meters where the sensor circuit and themeasurement electronics are housed together as a single unit, themeasurement circuit is often specifically calibrated for use with aparticular voltage and current sensors. The reason for the specificcalibration is that there can be significant error in signal response ofeach voltage and current sensors. In particular, the current sensingdevices, such as current transformers, often have a widely variablesignal response error. In other words, the signal response error of anytwo current sensing devices can vary to a significant degree. The signalresponse error of commonly available current transformers affects bothmagnitude and phase response.

The signal response error of such current transformers typically exceedsthe amount of energy measurement error that can be tolerated in themeter. In other words, while the current transformer signal responseerror may reach as much as 10%, the measurement error of the meter mustbe much less than 10%. Accordingly, compensation must be made for thevariance, or tolerance, of the current sensing devices to ensure thatthe ultimate energy measurement accuracy of the meter is withinacceptable tolerances. The compensation is typically carried out in theprior art by adjusting or calibrating the measurement circuit duringmanufacture to account for the signal response characteristics of thecurrent sensing devices that will be used in a particular meter unit. Inother words, each measurement circuit is custom-calibrated for eachmeter.

The meter assembly 10, however, should not require such extensiveunit-specific calibration. In other words, the sensor module 12 shouldbe able to receive any of a plurality of measurement meters 14 withoutextensive calibration operations. Accordingly, referring again to FIG.2, the sensor module 12 is pre-calibrated for modularity, such that thesensor module 12 may be coupled with any measurement module 14 withoutrequiring unit-specific calibration of that measurement module 14.

To this end, the sensor module 12, and specifically the voltage andcurrent sensors 15 are pre-calibrated such that the voltage and currentsensors 15 have a signal response within a tolerance of a predefinedsignal response that is no greater than the tolerance of the energymeasurement accuracy of the meter assembly 10. The energy measurementaccuracy of the meter assembly 10 may be defined as the accuracy of themeasured energy consumption with respect to the actual energyconsumption of the facility. Thus, if the tolerance of the energymeasurement accuracy of the meter is required to be 0.5%, then thedifference between the measured energy consumption and the actual energyconsumption will not exceed 0.5%. In such a case, the tolerance of thesignal response of the voltage and current sensors will be no more than,and typically substantially better than, 0.5%. As a result, themeasurement module 14 may readily be replaced with another measurementmodule without requiring specific calibration of the replacementmeasurement module.

The pre-calibration of the voltage and current sensors 15 may beaccomplished using careful manufacturing processes. The primary sourceof variance in the signal response of the voltage and current sensors 15is the signal response of the current transformers 16 a and 16 b.Generally available current transformers are prone to variance in bothmagnitude and phase angle signal response. Accordingly, pre-calibrationinvolves using current transformers that are manufactured to performwithin the required tolerances. As an initial matter, the currenttransformers 16 a and 16 b are manufactured using a high permeabilitycore material, which reduces phase angle variance in the signalresponse. Moreover, the current transformers 16 a and 16 b aremanufactured such that the actual number of turns is closely controlled.Close manufacturing control over the number of turns in the currenttransformers 16 a and 16 b produces sufficient consistency in themagnitude signal response to allow for interchangeability.

Alternatively, if controlling the number of turns during initialmanufacturing is not desirable for cost reasons, then turns may be addedor removed after manufacturing to achieve the desired signal response.For example, it may be more cost effective to buy wide tolerancecommercially available current transformers and adjust the number ofturns than to have sufficiently narrow tolerance current transformersspecially manufactured.

Still another method of obtaining calibration would be to useinexpensive wide tolerance current sensing devices and then storecalibration information directly in the sensor module 12 that may becommunicated to each measurement module 14 as it is connected. Such anarrangement in a modular meter is described in U.S. patent applicationSer. No. 60/325,030, filed Sep. 25, 2001, which is incorporated hereinby reference.

Referring now to the circuit block diagram in FIG. 6 of the sensormodule 12 of FIG. 2, the sockets 30 a and 30 b provide a connection tothe first current transformer 16 a, the sockets 30 e and 30 f provide aconnection to the second current transformer 16 b, the socket 30 cprovides a connection to the current blade 24 a, the socket 30 dprovides a connection to the current blade 24 b, and the socket 30 gprovides a connection to one or more of the neutral blades 20.

The sensor module 12 further includes the service disconnect switch 25.As shown herein, the service disconnect switch 25 includes a firstswitching contact 25 a and a second switching contact 25 b. The servicedisconnect switch further includes control signal lines 25 c and 25 dthat are operably coupled to the driver circuit 210.

In an ordinary residential “single phase” meter, the current blade 24 aconnects to a first high side of a 240-volt incoming utility power lineand the current blade 24 b connects to a second high side of the240-volt incoming utility power line. The utility current blade 24 aconnects through the first switching contacts 25 a to a first feederline of the customer load via the current blade 22 a. Similarly, theutility current blade 24 b connects through the second switchingcontacts 25 b to a second feeder line of the customer load via thecurrent blade 22 b. The current transformer 16 a is disposed in acurrent sensing relationship with the current flowing to the firstfeeder line through the current blade 22 a. The current transformer 16 bis disposed in a current sensing relationship with the current flowingthrough the second feeder line through the current blade 22 b.

The driver circuit 210 is operably coupled to communicate to an externaldevice, and namely, the measurement module 14, through the connectorribbon assembly 88. The driver circuit 210 is further connected toprovide control signals the switching contacts via signal lines 25 c and25 d. The driver circuit 210 is operably connected to controllablyenergize the indicators 52 and 54, and to detect actuation of any of theactuators 56, 78 and 80.

FIG. 7 shows in further detail a schematic of the elements of the drivercircuit board 23 including primarily the driver circuit 210. In additionto the driver circuit 210, as discussed above in connection with FIG. 2,the driver circuit board 23 further includes the actuators 78 and 80 andthe connector block 88 a.

The driver circuit 210 includes a digital control circuit 212,timer/clock circuitry 213, a power supply circuit 214, a voltage sensecircuit 216, I/O interface circuitry 218, external interface drivecircuitry 220 and disconnect switch drive circuitry 222.

The power supply circuit 214 is preferably coupled to the current blades24 a and 24 b to obtain external power even when the service disconnectswitch 25 is open (in the disconnected state or armed state). The powersupply circuit includes a transformer 224, a diode bridge circuit 223,and regulator circuit 225 configured as is well known in the art toprovide a DC power supply output voltage VCC derived from an AC inputvoltage.

The voltage sense circuit 216 is a circuit operably coupled to sensewhether line voltage is present on the feeder lines of the customerload. To this end, the voltage sense circuit 216 includes inputs 226 and228 electrically connected to the current blades 22 a and 22 b (see FIG.6) to obtain any voltages present in the feeder lines to the customerload. The input 226 connects to the input 228 through a resistivenetwork 230 and a bi-directional input 232 of an optical isolationcircuit 234. As a result, a voltage divider is formed at the input 232of the optical isolation circuit 234 by the resistive network 230 andthe inherent impedance of the bi-directional input 232.

It will be appreciated that the resistive network 230 may suitably beone or many resistors, so long as the total resistance value is selectedto provide an appropriate amount of drop over the bi-directional input232 at a relatively low current. Moreover, it will be noted that anadditional resistor may be coupled across the bi-directional input 232if necessary to reduce the drop over the bi-directional input 232.

The optical receiver/output 236 of the optical isolation circuit 234 iscoupled between the power supply voltage VCC and an output EXT1 of theconnector block 88 a. A capacitor 238 is coupled between the output EXT1and ground. Accordingly, when the input 232 of the optical isolation isbiased on, then the optical receiver/output 236 propagates the VCCsupply voltage (logic high) to the output EXT1, also charging thecapacitor 238. When the input 232 is not biased on, then the opticalreceiver/output 236 opens the connection between the VCC supply voltageand the output EXT1. The capacitor 238 discharges and then little or novoltage (logic low) propagates to the output EXT1. In general, theoutput EXT1 is provided to the processing circuitry in the measurementmodule 14 to aid in the detection of a form of tampering in which thesensor module 12 and/or the disconnect switch 25 is bypassed.

The timer/clock circuitry 213 comprises timer circuitry that providesclocking signals to the digital control circuit 212. Such devices arewell known. The I/O interface circuitry 218 provides buffer circuitrythat allows the digital control circuit 212 to receive input from andprovide output to various devices. For example, the I/O interface 218allows for a bi-directional serial data communication line to theprocessing circuitry of the measurement module 14 through the connectorblock 88 a. The I/O interface 218 also operably provides the digitalcontrol signal 212 with a signal representative of the status of theactuators 78 and 80. The external interface drive circuitry 220 providesthe drive circuitry necessary to cause the indicators 52, 54, which inthe exemplary embodiment described herein are light emitting diodes(“LEDs”), to illuminate in response to appropriate digital outputsignals generated by the digital control circuit 212. The externalinterface drive circuitry 220 further enables the digital controlcircuit 212 to obtain a digital signal representative of the status ofthe actuator 56.

The disconnect switch drive circuit 222 includes circuitry that enablesthe digital control circuit 212 to cause the switch contacts 25 a and 25b to open and close. In particular, the digital control circuit 212includes a CLOSE output and an OPEN output. The CLOSE output is coupledto the input/transmitter 250 of an optical isolation circuit 252 and theOPEN output is coupled to the input/transmitter 254 of an opticalisolation circuit 256. The output/receivers 258, 260 of the opticalisolation circuits 252, 256 respectively, are coupled to first andsecond AC power line voltages (i.e. the line voltages on current blades24 a and 24 b) in a manner configured to generate relatively high powercontrol signals at an output connector 262. For example, theoutput/receiver 258 allows AC power line current to flow temporarily tothe connector 262 and the output/receiver 260 allows AC power linecurrent to flow temporarily from the connector 262. The output connector262 is coupled to the control lines 25 c and 25 d of the disconnectswitch 25.

In general, the disconnect switch drive circuit 222 operates to providethe AC power line control signal to the control lines 25 c and 25 d thatsignal causes the switch contacts 25 a and 25 b to open responsive to alogic high signal on the OPEN output of the digital control circuit 212.The disconnect drive circuit 22 further operates to provide the AC powerline control signal to the control lines 25 c and 25 d that causes theswitch contacts 25 a and 25 b to close responsive to a logic high signalon the CLOSE output of the digital control circuit 212.

The digital control circuit 212 may suitably comprise a processor or oneor more programmable logic devices operably to carry out basic logicalfunctions in the control of the service disconnect switch 25, and theindicators 52 and 54. The digital control circuit 212 and the servicedisconnect switch 25 form a service disconnect circuit having adisconnected state, an armed state, and a connected state. The digitalcontrol circuit 212 generally controls the change of states of thecircuit and the outputs generated as a result of such changes in state.

In particular, the digital control circuit 212 is operable to changefrom the connected state to the disconnected state, from thedisconnected state to the armed state, and from the armed state to theconnected state. In general, the digital control circuit 212 causes theswitch contacts 25 a and 25 b to be open when transitioning into thedisconnected state, thereby disconnecting the electrical service to theload. The digital control circuit 212 further causes the switch contacts25 a and 25 b to be closed, thereby restoring service to the load whentransitioning from the armed state to the connected state. In the armedstate, the digital control circuit 212 leaves the switch contacts 25 aand 25 b open.

The digital control circuit 212 changes state in response to variety ofinputs. In general, the digital control circuit 212 changes from theconnected state to the disconnected state in response to serialcommunication signals received from the processing circuit of themeasurement module 14 (i.e. the processor or controller 48 of FIG. 8)through the connector block 88 a. The digital control circuit 212 alsochanges from the connected state to the disconnected state in responseto actuation of the actuator 78, which operates as a disconnect switch.In response to the change from the connected state to the disconnectedstate, the digital control circuit 212 generates a logic high signal onits OPEN output, thereby causing the switch contacts 25 a and 25 b toopen. In addition, the digital control circuit 212 generates a logichigh signal on the output that causes the indicator 52 to becomeilluminated. Finally, the digital control circuit 212 generates a signalidentifying the change in state to the processor 48 of the measurementmodule 14 via the connector block 88 a.

The digital control circuit 212 changes from the disconnected state tothe armed state in response to serial communication signals receivedfrom the processor 48 of the measurement module 14 through the connectorblock 88 a. The digital control circuit 212 also changes from thedisconnected state to the armed state in response to actuation of theactuator 80, which operates as an arm switch. In response to the changefrom the disconnected state to the armed state, the digital controlcircuit 212 generates a logic high signal on the output that causes theindicator 54 to become illuminated, and further stops generating thelogic high signal on the output that causes the indicator 52 to beilluminated. In addition, the digital control circuit 212 generates asignal identifying the change in state to the processor 48 of themeasurement module 14 via the connector block 88 a.

The digital control circuit 212 changes from the armed state to theconnected state in response to serial communication signals receivedfrom the processor 48 of the measurement module 14 through the connectorblock 88 a. The digital control circuit 212 also changes from the armedstate to the connected state in response to actuation of the actuator56, which operates as a connect switch. In response to the change fromthe armed state to the connected state, the digital control circuit 212generates a logic high signal on its CLOSE output, thereby causing theswitch contacts 25 a and 25 b to close. In addition, the digital controlcircuit 212 stops generating the logic high signal on the output thatcauses the indicator 52 to become illuminated. Finally, the digitalcontrol circuit 212 generates a signal identifying the change in stateto the processor 48 of the measurement module 14 via the connector block88 a.

The digital control circuit 212 may also monitor the mechanical positionof the switch 25 in an independent manner. In particular, the digitalcontrol circuit 212 may include a connection through the switch contacts25 a and/or 25 b which provide the digital control circuit 212 withfeedback as to the physical position of the switch contacts 25 a and 25b. In this manner, the digital control circuit 212 may ensure that theswitch 25 is operating properly.

FIG. 8 shows a circuit block diagram of the measurement circuit 42 andassociated display 38 for use in the measurement module 14. Themeasurement circuit 42 includes a watt measurement integrated circuit(“IC”) 44, a controller or processor 48, a non-volatile memory 50 andone or more communication circuits 51. Plugs 40 a, 40 b, 40 c, 40 d, 40e, and 40 f are each connected to the watt measurement IC 44 throughvarious input circuits. In particular, the plugs 40 a and 40 b areconnected to the watt measurement IC 44 through a current input circuit312, the plugs 40 e and 40 f are connected to the watt measurement IC 44through a current input circuit 314, the plug 40 c is connected to thewatt measurement IC 44 through a voltage input circuit 316, and the plug40 d is connected to the watt measurement IC 44 through a voltage inputcircuit 318.

The current input circuit 312 is a device configured to obtain a scaledsignal indicative of the line current waveform on the first feeder line.To this end, the current input circuit 312 is connected across a lineresistor RLA1 that is series connected between the plug 40 a and theplug 40 b. Plugs 40 a and 40 b, as discussed above and shown in FIGS. 2and 8, are electrically connected to the first current transformer 16 aof the sensor module 12. Similarly, the current input circuit 314 is adevice configured to obtain a scaled signal indicative of the linecurrent waveform on the second feeder line. To this end, the currentinput circuit 314 is connected across a line resistor RLA2 that isseries connected between the plug 40 e and the plug 40 f. Plugs 40 e and40 f, analogous to plugs 40 a and 40 b, are electrically connected tothe second current transformer 16 b of the sensor module 12. The outputsof the current input circuits 312 and 314 are provided to the wattmeasurement IC 44.

The voltage input circuit 316 is a voltage divider network tapped off ofthe connection to plug 40 c. Similarly, the input circuit 318 is avoltage divider network tapped off of the connection to the plug 40 d.The power supply 49 is a device that receives AC input line voltage andgenerates a DC supply voltage VDD therefrom. Such power supplies arewell known in the art. The power input to the power supply 49 ispreferably tapped off of the connection to the plug 40 d. The outputs ofthe voltage input circuits 316 and 318 are provided to the wattmeasurement IC 44.

The watt measurement IC 44 is a device that receives measurement signalsrepresentative of voltage and current signals in an electrical systemand generates energy consumption data therefrom. In the exemplaryembodiment described herein, the watt measurement IC 44 may suitably bethe conversion circuit 106 described in U.S. Pat. No. 6,112,158 or theconversion circuit 106 described in U.S. Pat. No. 6,112,159, both ofwhich are assigned to the assignee of the present invention andincorporated herein by reference.

Alternatively, the watt measurement IC 44 may be replaced by one or morediscrete circuits capable of carrying out the same function ofgenerating energy consumption information from the voltage and currentmeasurement signals. For example, the watt measurement IC 44 maysuitably be replaced by the first and second watt measurement ICs 44 and46 described in the U.S. Pat. No. 5,933,004, which is incorporatedherein by reference.

In any event, the watt measurement IC 44 is further operably connectedto the microcontroller 48 through a bus structure 320. The bus structure320 consists of one or more serial and or parallel busses that allow fordata communication between the microcontroller 48 and the wattmeasurement IC 44. In general, the watt measurement IC 44 providesenergy consumption data to the microcontroller 48 and themicrocontroller 48 provides control and calibration data to the wattmeasurement IC 44.

The microcontroller 48 is further operably connected to the memory 50,the communication circuit(s) 51, and the display circuit 38. Theprocessor 48 is also operably coupled to communicate with the sensormodule 12, and more particularly, the digital control circuit 212 of theservice disconnect switch circuit (See FIGS. 6, 7) using serial datasignals. To effect such communication, the processor 48 is operablycoupled to communicate such signals through the connector block 88 c.

In the operation of the exemplary meter assembly 10 illustrated in FIGS.2–8, energy consumption measurements are carried out in the followingmanner. As discussed above, the present embodiment is intended for usewith a wiring configuration commonly referred to in the industry as asingle-phase three-wire configuration. A single phase three-wireconfiguration, as discussed above, typically includes a 240 volt linethat is bisected into two 120 volt lines for use by the load, referredto herein as the First line and the Second line. The present invention,however, is in no way limited to use in single-phase configurations. Theconcepts described herein may readily be implemented in meters used inother configurations, including polyphase configurations.

In operation, the plurality of jaws 22 provide the first bisected powerline or First line signal across the blades 22 a and 24 a through theswitch contact 25 a (see FIGS. 2, 3 and 6). Similarly, the plurality ofjaws 22 provide the second bisected power line or Second line signalacross the blades 22 b and 24 b through the switch contact 25 b (seeFIGS. 2, 3 and 6). Referring to FIG. 6, the First line current flowsfrom the blade 24 a through the switch contact 25 a to the blade 22 a.The current blade 22 a, which passes through the current transformer 16a, imposes a scaled version of the current, referred to herein as thefirst current measurement signal, on the first current transformer 16 a.The first current measurement signal is approximately equal to thecurrent flowing through the current blade 22 a scaled by a factor of N1,where N1 is the turns ratio of the current transformer 16 a. The firstcurrent measurement signal is provided to the sockets 30 a and 30 b. Thefirst contact blade 24 a is further provides the first voltagemeasurement signal (i.e. the actual voltage of the First line) to thesocket 30 c.

Similar to the First line current, the Second line current flows fromthe blade 24 b through the switch contact 25 b to the current blade 22b. The current blade 22 b, which passes through the second currenttransformer 16 b, imposes a scaled version of the Second line currentonto the second current transformer 16 b, thereby causing the secondcurrent transformer 16 b to generate a second current measurementsignal. The second current measurement signal is approximately equal tothe Second line current scaled by a factor of N2, where N2 is the turnsratio of the second current transformer 16 b. The turn ratios N1 and N2of the current transformers 16 a and 16 b, respectively, are typicallysubstantially similar and preferably equal. However, manufacturingtolerances may result in slight differences in the turn ratios N1 andN2. In any event, the second current transformer 16 b provides thesecond current measurement signal to the sockets 30 e and 30 f. Theblade 24 b also provides the second voltage measurement signal (i.e. theactual voltage line signal) to the socket 30 d. The neutral blade 20provides a connection between the neutral power line and the socket 30g.

It is noted that potentially hazardous electrical signals reside on oneor more of the sockets 30 a through 30 g. In particular, the sockets 30c and 30 d provide a direct connection to the external or utility powerline, and therefore are potentially extremely dangerous. Moreover, thesockets 30 a, 30 b, 30 e, and 30 f all include current measurementsignals that are potentially dangerous to humans, depending somewhat onthe overall power consumption of the facility being metered and the turnratios N1 and N2. Accordingly, the relatively small physical size of thesockets 30 a through 30 g and their corresponding openings greatlyinhibits and preferably prevents human contact with the socketconnections.

Continuing with the general operation of the meter 10, the sockets 30 aand 30 b (FIG. 6) provide the first current measurement signal to theplugs 40 a and 40 b, respectively, of the measurement module 14 (FIG.8). Likewise, the sockets 30 e and 30 f (FIG. 6) provide the secondcurrent measurement signal to the plugs 40 e and 40 f, respectively, ofthe measurement module 14 (FIG. 8). The sockets 30 c and 30 d (FIG. 6),provide, respectively, the first and second voltage measurement signalsto the plugs 40 c and 40 d (FIG. 8). The neutral socket 30 g (FIG. 6)provides a neutral connection to the plug 40 g of FIG. 8.

Referring again to FIG. 8, at least the basic metering functions areprovided by the measurement circuit 42 within the measurement module 14.It will be noted, however, that the “basic metering functions” of themeasurement circuit 42 may include far more than simple energymeasurement functions. For example, the basic metering functionsprovided by the measurement circuit 42 may include at least a part ofone or more advanced features typically associated with electricitymeters, such as time of use metering, load profiling, demand metering,as well as other features such as service type recognition, diagnostics,remote meter reading communications or the like.

In any event, the plugs 40 a and 40 b provide the first currentmeasurement signal to the watt measurement IC 44 through the currentinput circuit 312. The current input circuit 312 preferably converts thefirst current measurement signal to a voltage signal having a magnitudeand phase that is representative of the First line current. The socket40 c provides the first voltage measurement signal through the voltageinput circuit 316 to the watt measurement IC 44.

The plugs 40 e and 40 f similarly provide the second current measurementsignal to the watt measurement IC 44 through the current input circuit314. The current input circuit 314 preferably converts the secondcurrent measurement signal to a voltage signal having a magnitude andphase that is representative of the Second line current. The socket 40 dprovides the second voltage measurement signal through the voltage inputcircuit 318 to the watt measurement IC 44. The socket 40 d furtherprovides the Second line voltage to the power supply 49. The powersupply 49 is further connected to the neutral plug 40 g and operates toprovide a supply voltage VDD to each of the functional block circuitswithin the measurement module 14.

The watt measurement IC 44 receives the voltage and current measurementsignals, and generates energy consumption data therefrom. To this end,the watt measurement IC 44 preferably samples, multiplies andaccumulates the measurement signals as is known in the art to generatewatt data, VA data, and/or VAR data. See, for example, U.S. Pat. No.6,112,158 or U.S. Pat. No. 6,112,159, as discussed above, for adescription of such operations.

The processor 48 then obtains watt data, VA data, and/or VAR data andfurther processes the data to provide energy consumption information instandard units in accordance with metering industry standards. Theenergy consumption information is communicated externally through thedisplay 38. Alternatively or additionally, the energy consumptioninformation may be communicated through the external communicationcircuit 51.

It is noted that in the exemplary embodiment described herein, the meter10 is a type of meter commonly known in the industry as a self-containedmeter. In a self-contained meter, the current coils of the meter, suchas current blades 22 a and 22 b of the present embodiment, carry theentire current load of the electrical system. As a result, in a typicalmeter, if the meter is removed for repair or replacement, the currentcoils are removed from the jaws of the meter box, and power to thefacility is interrupted. A distinct advantage of the present inventionis that the measurement module 14 may be removed for repair, replacementor upgrade without removing the current coils of the meter. As a result,the facility experiences no electrical service interruption during thereplacement.

Automated Operation of Service Disconnect Circuit

As discussed further above, it may be advantageous in some circumstancesto disconnect electrical service to the load connected to the meter 10.For example, an electrical service provider may employ remotedisconnection of service to periodically disconnect the load fordelinquent payors. To this end, disconnection and arm signals may bereceived from the service provider's systems via the communicationcircuits 51. In such a case, the communication circuit(s) 51 may includea telephone modem, power line carrier communication circuit, and/or aradio communication circuit. In an alternative embodiment, it may beadvantageous to disconnect electrical service to a load in a prepaidenergy system. The disconnection would be employed when the prepaidenergy quantity was consumed. In such a case, the controller orprocessor 48 may automatically track consumption of prepaid amounts anddisconnect service when appropriate. In another alternative, theprocessor 48 may automatically cause electrical service to bedisconnected in response to energy rationing processes enabled withinthe processor 48.

Regardless of whether the processor 48 receives service disconnectcircuit control signals from an external device or internally generatessuch control signals, the processor 48 provides corresponding disconnectcontrol signals to the digital control circuit 212 (see FIGS. 6, 7, and8) via the connectors 88 c and 88 a.

The digital control circuit 212 changes from the connected state to thedisconnected state upon receiving the disconnect control signal from theprocessor 48. During the state change, the digital control circuit 212operates as discussed above in connection with FIG. 7 to cause theswitch contacts 25 a and 25 b to open and to cause the indicator 52 tobe illuminated. The illuminated indicator 52 provides the customer (orother party) with a visual indication that service has been disconnectedvia the service disconnect circuit of the meter 10.

At some subsequent time, the processor 48 will provide an arm commandsignal to the digital control circuit 212. For example, the processor 48may be programmed to allow reconnection of electrical service after abrief interruption of service, upon full or partial payment of amountsdue, or upon subsequent prepurchase of additional energy. To allowreconnection of the electrical service to the load, the processorprovides the arm control signal to the digital control circuit 212 ofthe service disconnect circuit through the connectors 88 a and 88 c.

As discussed above, the digital control circuit 212 changes from thedisconnected state to the armed state upon receiving the arm commandsignal from the processor 48. The digital control circuit 212 operatesas discussed above in connection with FIG. 7 to illuminate the indicator54. The illuminated indicator 54 provides the customer (or other party)with a visual indication that service may now be re-connected becausethe service disconnect circuit of the meter 10 has been armed.

In accordance with one aspect of the present invention, the digitalcontrol circuit 212 may only be changed from the armed state to theconnected state through actuation of the actuator 56. In this manner,the dangers associated with remote or automatic reconnection ofelectrical service may be avoided. Moreover, the customer may avoidadditional unnecessarily costs of electricity consumption by having thechoice of whether to reconnect.

It is noted that in some prepaid energy situations, a smart card ordebit card may be inserted into a device that communicates with themeter locally. In such a case, the acceptance of prepayment could causethe digital control circuit 212 to change to the armed state andconnected state immediately.

However, in a normal situation which requires actuation of the connectactuator 56, the digital control circuit 212 detects the actuation andchanges from the armed state to the connected state. The digital controlcircuit 212 operates as discussed above in connection with FIG. 7 toclose the switch contacts 25 a and 25 b. When the switch contacts 25 aand 25 b are closed, then electrical power flows to the load connectedto the blades 22 a and 22 b from the power lines connected to the blades24 a and 24 b.

Manual Operation of Service Disconnect Circuit

In some circumstances, it may be advantageous to allow a technician theability to disconnect electrical service to the load connected to themeter 10 using the service disconnect circuit. To this end, the meter 10includes disconnect and arm switches in the forms of actuators 78 and80. However, the actuators 78 and 80 are not accessible to the customerbecause the measurement module 14 inhibits such access when installed onthe sensor module 12 (see FIGS. 1 and 2).

In order to access the actuators 78 and 80, the measurement module 14must be removed from the sensor module 12. Such removal typically causesa tamper event to occur. For example, removal of the measurement module14 may require compromise of a mechanical tamper seal that can only bereplaced by a qualified technician. Thus, access to the actuators 78 and80 is effectively limited to qualified technicians.

In the event that a technician needs to perform an operation in whichthe technician needs to either disconnect or reconnect the electricalservice, the technician first removes the measurement module 14 from thesensor module 12. The technician then actuates the disconnect switch 78if disconnection of service is desired or the arm switch 80 ifreconnection of service is desired. In the case of reconnection, thetechnician would further actuate the connect switch 56 to cause power tobe connected.

In further detail, when the technician actuates the disconnect switch78, the digital control circuit 212 detects the actuation and changesfrom the connected state to the disconnected state in response thereto.The digital control circuit 212 operates as discussed above inconnection with FIG. 7 to cause the switch contacts 25 a and 25 b toopen and to cause the indicator 52 to be illuminated. The indicator 52provides the technician with a visual indication that service has beendisconnected via the service disconnect circuit of the meter 10.

When the technician actuates the arm switch 80, the digital controlcircuit 212 detects the actuation and changes from the disconnectedstate to the armed state in response thereto. The digital controlcircuit 212 operates as discussed above in connection with FIG. 7 toilluminate the indicator 54. The indicator 54 provides the technicianwith a visual indication that service may now be re-connected becausethe service disconnect circuit of the meter 10 has been armed.

When the technician (or other party) actuates the connect actuator 56,the digital control circuit 212 detects the actuation and changes fromthe armed state to the connected state. The digital control circuit 212operates as discussed above in connection with FIG. 7 to close theswitch contacts 25 a and 25 b. When the switch contacts 25 a and 25 bare closed, then electrical power flows to the load connected to theblades 22 a and 22 b from the power lines connected to the blades 24 aand 24 b.

The technician may cycle through multiple disconnection and reconnectionoperations, as desired, before replacing the measurement module 14.

Bypass Tamper Protection

As discussed above, one method of tampering that can defeat theoperation of the service disconnect circuit of the meter 10 consists ofimplementing a bypass connection in parallel to the service disconnectswitch contacts 25 a and/or 25 b. In accordance with one aspect of thepresent invention, the processor 48 of the measurement module 14cooperates with the voltage sense circuit 216 of the driver circuit 210to sense such bypass connections.

In general, the voltage sense circuit 216 is operable to provide a logicsignal that is representative of whether line voltage is present on thefeeder lines to the customer's load. Referring to FIGS. 6 and 7, whenline voltage is present on the feeder lines, line voltage is alsopresent on the blades 22 a and 22 b. The voltage sense circuit inputs226 and 228 are electrically coupled to and thus obtain the line voltagefrom the blades 22 a and 22 b. The resistor network 230 of the voltagesense circuit 216 divides the line voltage and provides the divided linevoltage to the optical isolator bi-directional input 232. The dividedline voltage, which has a normal 50 or 60 Hz cycle, causes the one oftwo diodes of the bi-directional input 232 to be biased on through theentire AC cycle of the line voltage, except for the portions of the ACcycle directly adjacent to the zero crossings.

Because the bi-directional input 232 is biased on in such a manner, thereceiver/output 236 causes VCC to be connected to the output EXT1through most of the AC cycle. Moreover, during the short time near thezero crossings of the AC cycle in which the bi-directional input 232 isbiased off, the capacitor 238 sustains the high logic level at EXT1.Thus, EXT1 remains at a constant high logic state while line voltage ispresent on the blades 22 a and 22 b.

When line voltage is not present on the feeder lines, then no voltage ispresent on the blades 22 a and 22 b, nor the voltage sense inputcircuits 226 and 228. As a result, the bi-directional input 232 isbiased off and, as a result, the receiver/output 236 does not connectVCC to the output EXT1.

The processor 48 uses the EXT1 output and the state of the servicedisconnect switch 25 to determine whether a tamper event has occurred.If the service disconnect switch 25 is open and EXT1 is at a high logiclevel, then the processor 48 records a tamper event. It will be apparentthat when the service disconnect switch 25 is closed, EXT1 will be at ahigh logic level because line voltage is present at the load. However,no tamper event is recorded (at least in this tamper protectionoperation) because line voltage should be present when the servicedisconnect switch 25 is closed. The processor 48 obtains the state ofthe service disconnect switch 25 through the communication of the statechange by the digital control circuit 212 to the processor 48, discussedabove.

It will be appreciated that the tamper detection arrangement describedabove may readily be modified for use in non-modular meters. The tamperdetection arrangement advantageously requires only a single connectionto the processor 48, through the EXT1 connection (provided throughconnector assembly 88). The use of a single connection helps conservethe limited resource of processor inputs in utility meter circuitry.Such an advantage is particularly useful in modular meters (wherein theprocessor is located in another module), but is also useful in anyprocessor-based meter. Moreover, the implementation of an isolationmechanism provides additional advantages of complete isolation betweenthe power lines and the processor 48 useful in any meter design.

It will be appreciated that the above-described embodiments are merelyexemplary, and that those of ordinary skill in the art may readilydevise their own implementations that incorporate the spirit of thepresent inventions and fall within the spirit and scope thereof.

1. An apparatus for determining tampering in an electricity meterarrangement comprising: a service disconnect switch operable tocontrollably disconnect electrical power lines from a load, the loadincluding at least first and second feeder lines; a voltage sensecircuit coupled to sense voltage on the first and second feeder lines,the voltage sense circuit operable to generate a single voltagedetection signal based on a first voltage on the first feeder line and asecond voltage on the second feeder line, the voltage detection signalhaving a characteristic representative of whether line voltage from theelectrical power lines is present on the first and second feeder lines;and a processing circuit operably connected to the voltage sense circuitto receive the voltage detection signal, the processing circuit operableto selectively generate a tamper flag based on whether thecharacteristic of the voltage detection signal indicates the presence ofvoltage on the first and second feeder lines when the service disconnectswitch has disconnected the electrical power lines from the first andsecond feeder lines.
 2. The apparatus of claim 1 wherein the voltagesense circuit is further operable to generate a voltage detection signalhaving a first magnitude when line voltage is present on the first andsecond feeder lines and having a second magnitude when line voltage isnot present on the first and second feeder lines.
 3. The apparatus ofclaim 2 wherein the first magnitude and second magnitude are discretedigital signal levels.
 4. The apparatus of claim 1 wherein the voltagesense circuit includes a voltage divider operable to scale a voltagedifference between the first feeder line and the second feeder line. 5.The apparatus of claim 4 wherein: the voltage sense circuit furtherincludes an output switch; the voltage divider includes an outputcoupled to an output switch, the output switch biased on when thevoltage divider provides a voltage exceeding a predetermined level, theoutput switch operably coupled to provide the voltage detection signalto the processing device, the voltage detection signal varying based onwhether the output switch is biased on.
 6. The apparatus of claim 5wherein the processing circuit is further operable to obtain digitalvalues from a meter measurement circuit and generate meteringinformation therefrom.
 7. The apparatus of claim 1 wherein the voltagesense circuit includes an optical isolation circuit.
 8. The apparatus ofclaim 1, wherein the processing circuit includes a single input operablycoupled to receive the voltage detection signal.
 9. An apparatus fordetermining tampering in an electricity meter arrangement comprising: ahousing containing a metering circuit; a service disconnect switchdisposed within the housing, the service disconnect switch operable tocontrollably disconnect electrical power lines from a load, the loadincluding at least first and second feeder lines; a voltage sensecircuit coupled to sense voltage on at least one feeder line, thevoltage sense circuit including an isolation mechanism interposedbetween the at least one feeder line and an output to provide electricalisolation therebetween, the voltage sense circuit operable to generate avoltage detection signal having a characteristic representative ofwhether line voltage from the electrical power lines is present on theat least one feeder line, the voltage sense circuit operable to providethe voltage detection signal to the output; and a processing circuitoperably connected to the output to receive the voltage detectionsignal, the processing circuit operable to selectively generate a tamperflag based on whether the characteristic of the voltage detection signalindicates the presence of voltage on the at least one feeder line whenthe service disconnect switch has disconnected the electrical powerlines from the first and second feeder lines.
 10. The apparatus of claim9 wherein the voltage sense circuit is further operable to generate avoltage detection signal having a first magnitude when line voltage ispresent on the at least one feeder line and having a second magnitudewhen line voltage is not present on at least one feeder line.
 11. Theapparatus of claim 10 wherein the first magnitude and second magnitudeare discrete digital signal levels.
 12. The apparatus of claim 9 whereinthe voltage sense circuit includes an output switch, the output switchbiased on when line voltage is present on the at least one feeder line,the output switch operably coupled to provide the voltage detectionsignal to the output, the voltage detection signal varying based onwhether the output switch is biased on.
 13. The apparatus of claim 12wherein the output switch is an optical receiver, the optical receiverincluding a portion of the isolation mechanism.
 14. The apparatus ofclaim 9 wherein the isolation mechanism includes an optical isolationcircuit.
 15. A method comprising: a) disconnecting, using a servicedisconnect switch, at least one feeder line of a load from at least oneelectrical power line, the service disconnect switch disposed within anelectricity meter housing; b) employing a voltage sense circuit that isoperably connected to the at least one feeder line to generate a voltagedetection signal having a characteristic representative of whether linevoltage from the electrical power lines is present on the at least onefeeder line; c) providing the voltage detection signal to an output thatis electrically isolated from the at least one feeder line; d) employinga processing circuit to receive the voltage detection signal andgenerate a tamper flag if the characteristic of the voltage detectionsignal indicates the presence of line voltage on the at least one feederline.
 16. The method of claim 15 wherein step b) further includesemploying the voltage sense circuit to generate the voltage detectionsignal such that the voltage detection signal has a first magnitude whenline voltage is present on the at least one feeder lines and the voltagedetection signal has a second magnitude when line voltage is absent fromthe at least one feeder line.
 17. The method of claim 16 wherein step b)further includes employing the voltage sense circuit to generate thevoltage detection signal such that the first magnitude and the secondmagnitude are discrete digital voltage levels.
 18. The method of claim15 wherein step c) further comprises providing the voltage detectionsignal to the output using optical isolation.
 19. The method of claim15, wherein step c) further comprises employing the voltage sensecircuit to generate the voltage detection signal by generating thevoltage detection signal to have a characteristic that is representativeof a voltage differential between two feeder lines.